Here's the thing, take all personal testimony as false unless you witness it and record what happened.

There you go, I just made life much simpler for you.

There is an interesting effect in weight loss, but it applies to so many more things. That is when a lot of people diet they record particular things like how much they ate at a meal, but not how much they snacked. When you have a third party observer record everything that observer gets a much different calorie intake amount than the person dieting.

This is also true for almost any human claim that is not backed up by outside observation. We do all kinds of things subconsciously. We cut out any information that may look bad. The words we say have huge amounts of assumptions build in for 'us' but may not apply to anyone else on the planet. This is why science quite commonly finds reality is in direct opposition to how our minds think it works.

I honestly think this is some fundamental limit of single observer based intelligence.